More than 150 Sri Lankan asylum seekers who languished on an Australian customs vessel for weeks have been temporarily brought to a detention centre on Australia's mainland where their identities will be determined by Indian officials, a government minister has said.

Australia has made an exception for the 157 men, women and children from its tough policy of refusing to allow asylum seekers who attempt to reach the country by boat to ever set foot on the mainland.

They were on board an Indian-flagged ship from the south-east port of Pondicherry when they were intercepted by an Australian customs vessel in late June.

The immigration minister, Scott Morrison, said all of the asylum seekers had been flown overnight from the Cocos Islands, an Australian Indian Ocean territory midway between Sri Lanka and Australia, to the Curtin detention centre in Western Australia.

Indian consular officials would interview them there to determine their nationalities.

India has agreed to take back any of its citizens who might be on board, and would consider taking back Indian residents who might be Sri Lankan citizens, the Indian high commissioner to Australia, Biren Nanda, said.

Morrison told Australian Broadcasting Corp the asylum seekers did not risk persecution in India. He described their passage to Australia as "an economic migration seeking to illegally enter Australia".

He would not say what would happen to asylum seekers who were rejected by India, but insisted none would be resettled in Australia. Sending them to detention camps in the Pacific island nations of Papua New Guinea and Nauru were options.

"There are a very large number of people on this ship that had been resident in India for a very long time," Morrison told ABC.

Prime minister Tony Abbott's government has implemented a tough policy of turning back asylum seekers' boats in a bid to stop a surge in the number of vessels trying to reach Australian shores. No asylum seeker has successfully reached Australia by boat this year.